Advanced cellular communication networks (e.g. 4G Long Term Evolution) allow for deployment of small cell devices (e.g., microcell device, picocell device, femtocell device) that operate in a similar manner to a macro base station (e.g. high powered cellular base station or tower), but with a small cell coverage area that is less than a macro cell coverage area of the macro base station.
Referring to FIG. 1, is depicted a cellular communication network in which small cell devices 130A, 130B, and 130C, having respective small cell coverage areas 135A, 135B, and 135C, are deployed within macro cell coverage area 120 of a macro base station 110. Small cell devices 130A, 130B, and 130C can communicate with user equipment 140A, 140B, and 140C wirelessly. Small cell devices 130A, 130B, and 130C can communicate with macro base station 110 wirelessly or through wired connection 150 (e.g. backhaul connection).
It is to be appreciated that a small cell device can have different, less, or more operation states than a macro base station. Thus, it is possible for a small cell device to attain additional flexibility over a macro base station.
Referring to FIG. 2 is a non-limiting example of operation states of a small cell device (e.g. femto base station). In radiation power on/off state 210, small cell device can control radio frequency components to turn ON or OFF radiation power on one or more frequencies. In initialization state 220, such as transitioning from radiation power on/off state 210, small cell device can determine operational parameters for communication on the cellular communication network, such as in a non-limiting example, frequency subcarriers (e.g. channels) to employ and radiation power level for its radio antennae. In operational state 230, such as transitioning from initialization state 220, small cell device can operate in two modes, normal operation mode 240 and low duty mode 250. In normal operation mode 240, small cell device operates as a macro base station with a smaller cell coverage area. In low duty mode 250, small cell device turns off or reduces radiation power of its radio antennae periodically or aperiodically to decrease interference with neighboring small cell devices or macro base stations, where available interval state 260 does not have the radiation power reduced or turned off, and unavailable interval state 270 has the radiation power reduced or turned off. It is to be appreciated that small cell device can transition between states and modes as needed according to any suitable criteria or algorithm.
The deployment of a vast number of small devices can introduce several potential problems for the cellular communication networks. For example, interference can be an issue. In some cellular communication networks, all base stations (e.g., macro and small cell) broadcast system information within a fixed set of frequency subcarriers of a signal (e.g., orthogonal frequency division multiplexing). As such neighboring base stations can cause mutual interference on the set of subcarriers used for broadcasting system information. In another example, increased usage of limited bandwidth for transmitting control information can create inefficiencies. As a small cell generally services only a few user equipment, periodically broadcasting control information increases the bandwidth usage overhead per user equipment. As an additional example, inefficient usage of sub-frames in the downlink/uplink scheduling can also be an issue. The basic unit of downlink/uplink scheduling is per sub-frame. There is an increased possibility that a small cell device serves one or a low number of user equipment, therefore occupying an entire sub-frame in the downlink/uplink scheduling for the one or low number of user equipment.